In recent years, vehicles incorporating a power storage device (such as a secondary battery or capacitor) and running with driving power generated from electric power stored in the power storage device have been receiving attention as environmentally friendly vehicles. Examples of such vehicles include an electric vehicle, a hybrid vehicle, and a fuel cell vehicle.
There is a need to improve energy efficiency of these vehicles by increasing gasoline mileage and electric mileage, so as to further reduce environmental loads.
Japanese National Patent Publication No. 2008-520485 (PTD 1) discloses a hybrid vehicle including an internal combustion engine and a motor generator, in which the motor generator is controlled, when in a generator mode, in such a manner that the motor generator alternates between a first interval and a second interval. During the first interval, the motor generator is driven to operate with a high output which is greater than an actual power consumption of a vehicle electrical system. During the second interval, the motor generator is switched off.
According to Japanese National Patent Publication No. 2008-520485 (PTD 1), when the motor generator operates as a generator, the motor generator is driven at an operating point of high efficiency in the first interval and the motor generator is stopped in the second interval. As a result, continuation of the operation of the motor generator with low efficiency during operation of electric power generation can be suppressed, thus improving energy efficiency of the vehicle during the operation of electric power generation.
Japanese Patent Laying-Open No. 2010-6309 (PTD 2) discloses a hybrid vehicle including an internal combustion engine and a motor generator, which is configured to alternate between running with driving power generated by the internal combustion engine and running in a coasting state in which the internal combustion engine is stopped. As a result, the internal combustion engine can be driven at an operating point of high efficiency, thus increasing gasoline mileage.